Running SurvCE with Leica TCRA 1100 Robot.
Usually, I'm a two dimensional kind of guy, rarely carrying elevations around a traverse. On those rare occasions when I do topos, every single time my back-sight check is 0.04'-0.06' low. ALWAYS low. Distance is immaterial, ditto prism used.
F1-F2 Z angles always agree within 10", both ahead & back and yes, HI & HT very carefully measured. Now I'd expect a bit of slop, but I'd think it would be equally likely to be positive or negative, but it's always low.
Any ideas?
Thanks,
SS
your box tape made in china?
NEW Lufkin 6' folding rule; box tapes are for carpenters - Smarty-pants......
Brother, I am with you. I have been chasing my tail on this for years. TCA1100 (vintage 1998). SurveyPro on a Ranger. 360 prism.
Unfortunately I am no help though.
Commiseration font /off.
Collimation routine doesn't make any difference?
Are you using the 360 prism with the 3 arrows on alternating faces? If so, the prism face with an arrow over it needs to be facing the instrument for correct elevations to be carried through.
Does NOT matter which glass.
Leica 360, Leica circle, generic -30mm, -30mm peanut; mix 'em match 'em- don't matter a bit, BS check always 0.04'-0.06' LOW
> Are you using the 360 prism with the 3 arrows on alternating faces? If so, the prism face with an arrow over it needs to be facing the instrument for correct elevations to be carried through.
Even when I take that care (I have colored them with three different color paint marker dots ~ red, green, and blue - I always keep the red dot pointing at the gun) I still often get 0.03' error in the vertical back sight check after I move forward to the newly set FS point.
Could you isolate the problem to your controllers back sight check routine? If you were to measure the elevation to your back sight manually using the HI, HR & vertical difference, would you get the same resulting elevation difference?
> Could you isolate the problem to your controllers back sight check routine? If you were to measure the elevation to your back sight manually using the HI, HR & vertical difference, would you get the same resulting elevation difference?
Good idea. I "think" that when I do the BS check routine and it is out 0.03 and then I do the stakeout routine, I "think" I see that same error, maybe?
I will have to break out the auto level next time...
Sarge, what do you think?
Have you run a test traverse with the equipment you talked about and then checked that with a level or another total station?
Is the problem in the initial foresight recording to the next point or in the backsight shot or both?
If it's only one, that would be weird. Both sounds to me like a vertical collimation issue.
If in your level run, everything matches the initial shots you took, it's the backsights.
If the errors show up to be same as is shown in the backsight checks, it's only the foresights.
If the errors only seem to be half what is shown in the backsight checks, it's both (this is because you are accruing half the error in the foresight and then the other half in the backsight check).
Good luck with it.
Run the vertical calculations by hand. I have had two data collectors assume my gun height was on some ridiculous 'slant'...
If your glass is holding horizontal, are you pointing at the center of the glass or at the center of your HI? Since the center of the glass is not over your center of target you may not be getting your vertical angle to the right spot.
Hope what I am trying to say is understandable.
What I meant was don't use the controller. Measure with the same instrument in manual mode and see if the result is the same. That would isolate the problem to the dc or gun.
what are you shooting as the FS? graduated prism pole or tripod?
That appears to be a likely solution. There's probably a selection in the software for true height versus slant height.
The slant measurement is not ridiculous, just a different way of doing it. I've read that Leica sells a slant rule for use in determining HI of their instruments and prisms. It is graduated for the vertical component when the rule is held as the hypotenuse from the ground point to the side of the instrument.
> What I meant was don't use the controller. Measure with the same instrument in manual mode and see if the result is the same. That would isolate the problem to the dc or gun.
Gotcha, thanks.
:gammon:
Usually the problem by using a fixed prism or a tilt prism with face plate not being on the same plane with observed point, especially when elevation change is steep and prism not pointed directly at instrument.
Sometimes it is because you are collecting data with curvature of the earth checked on.
😉
Another quick thought is if you set the prism height to zero and took the shot, then inverse to the point elevation, the difference should be your measure up. If the HR is getting treated as a hypotenuse, you'll see the error there between the two heights.
That's what I was trying to say.
